Everyone knows that binary data encodings are much more efficient than the Extensible Markup Language (XML). Given that XMPP is an application profile of XML, it is a wonder that XMPP works at all! Clearly, XMPP would benefit from a binary representation. Therefore, this specification defines Binary XMPP.

It might be objected that the Binary XMPP representation requires a large number of XML elements. However, because all data is represented using only <zero/> and <one/>, the protocol can be significantly compressed using the standard ZLIB compression algorithm as defined in RFC 1950 [2], which SHOULD be enabled by default on the bxmpp port. Evidence from preliminary testing indicates that compression of Binary XMPP results in a representation less than 2% of the original size!

As a further simplification, Binary XMPP gets rid of the complicated stream negotiation process defined in RFC 3920. Instead, if a server supports Binary XMPP it advertises a special DNS SRV record _bxmpp._tcp in accordance with RFC 2782 [3]. Furthermore, only one record is needed, thus saving precious port space. The RECOMMENDED port for Binary XMPP communication is 10110, but any port MAY be used.

To start a Binary XMPP stream, the sender simply connects via TCP at the advertised port and starts sending <zero/> and <one/> elements. The lack of a stream header simplifies XML parsing, introducing further performance improvements.

The <zero/> and <one/> elements use English-language words as the element names. Clearly it would have been preferable to define an i18n-friendly binding, such that German-language applications could encode Binary XMPP using the <null/> and <eins/> elements, Greek-language applications could use the <μηδέν/> and <ἑνα/> elements, etc. Flexibility regarding internationalization of the element names may be added in Binary XMPP 2.0.

Appendix C: Legal Notices

Copyright

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

5. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.

6. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.